U.S. patent number 6,341,066 [Application Number 09/672,498] was granted by the patent office on 2002-01-22 for electronic control unit having drive element and control processing element.
This patent grant is currently assigned to Denso Corporation. Invention is credited to Taku Iida, Toru Murowaki, Yoshitaka Nakano, Toshiaki Yagura.
United States Patent |
6,341,066 |
Murowaki , et al. |
January 22, 2002 |
Electronic control unit having drive element and control processing
element
Abstract
In an electronic control unit, a drive element liable to
generate heat and a control processing element liable to be
affected by heat are respectively mounted on a drive circuit board
and a control circuit board different from each other, and the two
boards are connected to each other by a flexible printed circuit
board. The bonding portion of the flexible printed circuit board to
the control circuit board is a back side portion of a connector
mounted on the control circuit board at the same side as the
control processing element. Therefore, heat generated by the drive
element is suppressed from being transferred to the control
processing element without causing layout hindrances.
Inventors: |
Murowaki; Toru (Chiryu,
JP), Yagura; Toshiaki (Nakata-gun, JP),
Nakano; Yoshitaka (Chiryu, JP), Iida; Taku
(Kariya, JP) |
Assignee: |
Denso Corporation (Kariya,
JP)
|
Family
ID: |
27336644 |
Appl.
No.: |
09/672,498 |
Filed: |
September 29, 2000 |
Foreign Application Priority Data
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Sep 30, 1999 [JP] |
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11-279301 |
Oct 5, 1999 [JP] |
|
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11-284218 |
Oct 8, 1999 [JP] |
|
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11-288398 |
|
Current U.S.
Class: |
361/707; 257/723;
361/719; 361/789 |
Current CPC
Class: |
H05K
1/144 (20130101); H05K 7/20854 (20130101); H05K
7/209 (20130101); H01L 2924/181 (20130101); H01L
2224/48091 (20130101); H01L 2224/48247 (20130101); H01L
2224/73265 (20130101); H01L 2224/48091 (20130101); H01L
2924/00014 (20130101); H01L 2924/181 (20130101); H01L
2924/00012 (20130101) |
Current International
Class: |
H05K
7/20 (20060101); H05K 1/14 (20060101); H05K
007/20 () |
Field of
Search: |
;165/80.3,185
;257/687,691,706,707,712,713,723,724
;361/704,705,707,710,711,752,717-719,784,785,789
;29/832,840,841,856 ;438/108,122 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1-147850 |
|
Jun 1989 |
|
JP |
|
6-21330 |
|
Jan 1994 |
|
JP |
|
Primary Examiner: Tolin; G P
Attorney, Agent or Firm: Pillsbury Winthrop LLP
Claims
What is claimed is:
1. An electronic control unit comprising:
a box having an inner wall part serving as a radiation plate;
a drive circuit board disposed in close adhesion with the radiation
plate in the box;
a control circuit board disposed in the box and facing the drive
circuit board;
a connecting wire connecting the drive circuit board and the
control circuit board;
a connector disposed on the control circuit board;
a drive element disposed on the drive circuit board for supplying
power to an outside control object through the connector; and
a control processing element disposed on the control circuit board
for performing a control processing based on a signal inputted from
an outside of the box through the connector and outputting a
control signal in accordance with a result of the control
processing to the drive element to control the outside control
object, wherein the connecting wire is connected to the control
circuit board at a bonding portion in a vicinity of the connector;
and
wherein the connector integrally has a first connector pin and a
second connector pin, the first connector pin being electrically
connected to the drive element for transmitting the power from the
drive element to the outside control object, the second connector
pin being electrically connected to the control processing element
for transmitting the signal from the outside of the box to the
control processing element.
2. The electronic control unit according to claim 1, wherein:
the connector is disposed at a specific location on a first surface
of the control circuit board at an opposite side of the drive
circuit board; and
the bonding portion of the connecting wire to the control circuit
board is a back side portion of the specific location, on a second
surface of the control circuit board.
3. The electronic control unit according to claim 1, wherein the
connecting wire is bonded to an end part of the control circuit
board as the bonding portion and to an end part of the drive
circuit board.
4. The electronic control unit according to claim 1, wherein the
connecting wire is a flexible printed circuit board.
5. The electronic control unit according to claim 1, wherein the
drive circuit board is made of a material having a thermal
radiation property superior to that of the control circuit
board.
6. The electronic control unit according to claim 1, wherein:
the drive circuit board is made of a ceramic material; and
the control circuit board is made of a resin material.
7. The electronic control unit according to claim 1, wherein the
connecting wire is separated from a wall of the box.
8. The electronic control unit according to claim 1, wherein the
drive element disposed on the drive circuit board electrically
communicates with the outside control object inevitably via the
connecting wire and the connector disposed on the control circuit
board.
9. The electronic control unit according to claim 1, wherein the
drive circuit board is connected with the control circuit board at
only one end part thereof by the connecting wire.
10. The electronic control unit according to claim 1, wherein:
the control circuit board divides an inner space of the box into
first and second spaces;
the control processing element is disposed on the control circuit
board in the first space; and
the drive element is disposed on the drive circuit board in the
second space.
11. The electronic control unit according to claim 10, wherein the
drive circuit board has an area smaller than that of the control
circuit board.
12. An electronic control unit comprising:
a box having an inner wall part serving as a radiation plate;
a drive circuit board disposed in close adhesion with the radiation
plate in the box;
a control circuit board disposed in the box and facing the drive
circuit board;
a connecting wire connecting the drive circuit board and the
control circuit board, wherein the connecting wire is flexible
printed circuit board;
a connector disposed on the control circuit board;
a drive element disposed on the drive circuit board for supplying
power to an outside control object through the connector; and
a control processing element disposed on the control circuit board
for performing a control processing based on a signal inputted from
an outside of the box through the connector and outputting a
control signal in accordance with a result of the control
processing to the drive element to control the outside control
object, wherein
the connecting wire is connected to the control circuit board at a
bonding portion in a vicinity of the connector,
the flexible printed circuit board has a first interconnection
pattern constituting a power path extending from the drive element
to the control object through the connector, and a second
interconnection pattern constituting a control signal transmission
path extending from the control processing element to the drive
element, the first interconnection pattern being wider in width
than the second interconnection pattern.
13. An electronic control unit comprising:
a box having an inner wall part serving as a radiation plate;
a drive circuit board disposed in close adhesion with the radiation
plate in the box;
a control circuit board disposed in the box and facing the drive
circuit board;
a connecting wire connecting the drive circuit board and the
control circuit board, wherein the connecting wire is flexible
printed circuit board;
a connector disposed on the control circuit board;
a drive element disposed on the drive circuit board for supplying
power to an outside control object through the connector; and
a control processing element disposed on the control circuit board
for performing a control processing based on a signal inputted from
an outside of the box through the connector and outputting a
control signal in accordance with a result of the control
processing to the drive element to control the outside control
object, wherein
the connecting wire is connected to the control circuit board at a
bonding portion in a vicinity of the connector,
the electronic control unit is manufactured by:
disposing the drive circuit board on which the drive element is
mounted and the control circuit board on which the connector and
the control processing element are mounted to be lined up in an
identical plane,
electrically connecting the drive circuit board and the control
circuit board by soldering the flexible printed circuit board to
end parts of the drive circuit board and the control circuit board,
which are disposed side by side, from one side of the plane,
and
housing the drive circuit board and the control circuit board
connected to each other in the box such that the drive circuit
board and the control circuit board face each other.
14. The electronic control unit according to claim 13, wherein the
drive circuit board is bonded to the radiation plate before the
drive circuit board and the control circuit board are electrically
connected.
15. An electronic control unit comprising:
a box having an inner wall part serving as a radiation plate;
a drive circuit board disposed in close adhesion with the radiation
plate in the box;
a control circuit board disposed in the box and facing the drive
circuit board;
a connecting wire connecting the drive circuit board and the
control circuit board;
a connector disposed on the control circuit board;
a drive element disposed on the drive circuit board for supplying
power to an outside control object through the connector;
a control processing element disposed on the control circuit board
for performing a control processing based on a signal inputted from
an outside of the box through the connector and outputting a
control signal in accordance with a result of the control
processing to the drive element to control the outside control
object, wherein
the connecting wire is connected to the control circuit board at a
bonding portion in a vicinity of the connector,
the control circuit board divides an inner space of the box into
first and second spaces,
the control processing element is disposed on the control circuit
board in the first space,
the drive element is disposed on the drive circuit board in the
second space,
a heat interception plate is disposed in the second space and
divides the second space into third and fourth spaces for
preventing heat transfer between the third and fourth spaces,
wherein the drive element is disposed in the third space, and the
control processing element is disposed on the control circuit board
at an opposite side of the fourth space.
16. The electronic control unit according to claim 15, wherein the
heat interception plate is made of a resin material.
17. The electronic control unit according to claim 1, wherein:
the box has a board support portion on an inner wall thereof;
and
the control circuit board is supported by the board support portion
in the box.
18. An electronic control unit comprising:
a box having an inner wall part serving as a radiation plate;
a drive circuit board disposed in close adhesion with the radiation
plate in the box;
a control circuit board disposed in the box and facing the drive
circuit board;
a connecting wire connecting the drive circuit board and the
control circuit board;
a connector disposed on the control circuit board;
a drive element disposed on the drive circuit board for supplying
power to an outside control object through the connector; and
a control processing element disposed on the control circuit board
for performing a control processing based on asignal imputed from
an outside of the box through the connector and outputting a
control signal in accordance with a result of the control
processing to the drive element to control the outside control
object,
wherein the connecting wire is bonded to mutually facing end parts
of the control circuit board and the drive circuit board, is bent
to form a gap with a wall of the box, and has a length that allows
the control circuit board and the drive circuit board to be lined
up in an identical plane without an overlap.
19. The electronic control unit according to claim 18, wherein the
connecting wire is bent generally into a U-shape between the
control circuit board and the drive circuit board.
20. The electronic control unit according to claim 18, wherein the
connecting wire is bent with a plurality of folds between the
control circuit board and the drive circuit board.
21. The electronic control unit according to claim 18, wherein:
the connector is disposed on the control circuit board at an
opposite side of the drive circuit board, and is electrically
connected with the control circuit board through a connector pin
inserted into a through hole provided in the control circuit board;
and
the connecting wire is bonded to a bonding portion of the control
circuit board at a back side portion of the connector, and is bent
with a folded portion that is positioned at a side of the bonding
portion with respect to the connector pin.
22. The electronic control unit according to claim 18, further
comprising an electronic component disposed on the drive circuit
board, wherein:
the connecting wire connects the control circuit board and the
drive circuit board in the box to define a gap between the
electronic component and the control circuit board.
23. An electronic control unit comprising:
a box having an inner wall part serving as a radiation plate;
a drive circuit board disposed in close adhesion with the radiation
plate in the box;
a control circuit board disposed in the box to face the drive
circuit board, and electrically connected with the drive circuit
board;
a connector disposed on the control circuit board;
a drive element disposed on the drive circuit board for supplying
power to an outside control object through the connector; and
a control processing element disposed on the control circuit board
for performing a control processing based on a signal imputed from
an outside of the box through the connector and outputting a
control signal in accordance with a result of the control
processing to the drive element to control the outside control
object,
wherein the control processing element and the drive element are
disposed at opposite sides to each other with a plane interposed
therebetween, the plane being approximately perpendicular to the
inner wall part of the box on which the drive circuit board is
disposed.
24. The electronic control unit according to claim 23, further
comprising a heat interception plate extending from the inner wall
part of the box to the control circuit board to intercept heat
transfer from the drive element to the control processing
element.
25. The electronic control unit according to claim 23, wherein the
connector is disposed at a side of the drive element with respect
to the plane.
26. An electronic control unit comprising:
a box having an inner wall part serving as a radiation plate;
a drive circuit board disposed on the radiation plate in the
box;
a control circuit board disposed in the box and facing the drive
circuit board;
first and second connector pins fixed to the control circuit
board;
a connecting member connecting the drive circuit board and the
control circuit board;
a drive element disposed on the drive circuit board and
electrically connected to the first connector pin, for supplying
power to an outside control object through the first connector pin;
and
a control processing element disposed on the control circuit board
and electrically connected to the second connector pin, for
performing a control processing based on a signal inputted from an
outside of the box through the second connector pin and for
outputting a control signal in accordance with a result of the
control processing to the drive element to control the outside
control object, wherein
the first and second connector pins are provided on a same side of
the control circuit board as each other with respect to the drive
element.
27. The electronic control unit according to claim 26, wherein the
connecting member is connected to the control circuit board on the
same side of the control circuit board as the first and second
connector pins with respect to the drive element.
28. The electronic control unit according to claim 27, wherein the
first and second connector pins protrude from a common connector
disposed on the control circuit board.
29. The electronic control unit according to claim 28, wherein the
connector and the connecting member are respectively fixed to
opposite surfaces of the control circuit board on the same side
with respect to the drive element.
30. The electronic control unit according to claim 26, wherein the
drive element and the control processing element are electrically
connected to each other through the connecting member.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of Japanese
Patent Applications No. 11-279301 filed on Sep. 30, 1999, and No.
11-284218 filed on Oct. 5, 1999, and No. 11-288398 filed on Oct. 8,
1999, the contents of which are incorporated herein by
reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an electronic control unit for
drive-controlling an outside control object, and a manufacturing
method thereof.
2. Description of the Related Art
There have been known electronic control units (for example
electronic control units for mounting in vehicles, which perform
engine control or transmission control) for supplying electrical
power to and thereby driving outside control objects (for example
various actuators such as electromagnetic solenoids) and
controlling their operation.
This kind of electronic control unit, for example as shown in FIGS.
1A and 1B, is made by housing a connector 102, a control processing
element 103 and drive elements 105 in a box 107. The control
processing element 103 performs computational processing on the
basis of signals inputted from outside via the connector 102 and
outputs control signals. The control processing element 103 is for
example a CPU or a microcomputer. The drive elements 105 are for
being driven by control signals from the control processing element
103 and supplying power to outside control objects, and are for
example power transistors or power ICs.
In this kind of electronic control unit, from the point of view of
productivity improvement and cost reduction, the control processing
element 103 and the drive elements 105 have been mounted on the
same circuit board 109 as shown in FIGS. 1A and 1B. However, the
drive elements 105 handle large currents (i.e. electrical powers)
compared to the control processing element 103 and so on, and
produce a large amount of heat. On the other hand, the control
processing element 103, which performs various computational
processing, readily suffers influences of heat, and consequently
there is a possibility of heat produced by the drive elements 105
excessively raising the temperature of the control processing
element 103 and making its operation unstable.
Generally, because the circuit board 109 on which the control
processing element 103 and the drive elements 105 are mounted uses
a board made of resin having a relatively low thermal conductivity
among the various circuit boards, the positional relationship
between the two has been considered for example by separating the
control processing element 103 and the drive elements 105 as much
as possible on the board. By this being done, it has been made
difficult for heat produced by the drive elements 105 to reach the
control processing element 103. Incidentally, FIG. 1A shows the
construction of the electronic control unit as seen from a
direction parallel with the board face of the circuit board 109,
and FIG. 1B shows the electronic control unit as seen from a
direction perpendicular to the board face of the circuit board
109.
However, in electronic control units of recent years, due to
complicated and multifunctionalized control content, the increase
in number of the drive elements 105 and the increase in power
handled by the drive elements 105 have progressed. Further, along
with this the amount of heat produced in the drive elements 105 is
in an increasing trend. In this case, it is conceivable to suppress
thermal influences on the control processing element 103 by making
the circuit board 109 larger and further separating the control
processing element 103 from the drive elements 105. However, when
the space for mounting the electronic control unit is restricted
(for example in cases such as when the electronic control unit is
to be mounted in a vehicle), there is a limit from the point of
view of saving space. Further, when the area of the circuit board
109 is made large, the manufacturing yield of the circuit board 109
deteriorates, and as a result the manufacturing cost of the
electronic control unit can be increased.
Because of this in electronic control units of recent years it has
been becoming not easy to suppress thermal influences affected on
the control processing element 103 by heat produced in the drive
elements 105. Further, as the amount of heat produced in the drive
elements 105 increases, it may exceed the limit of the thermal
radiation capacity in the electronic control unit. In such case,
heat produced in the drive elements 105 is not sufficiently
dissipated, and not only the control processing element 103 but
also the operation of the drive elements 105 may become
unstable.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above problems.
An object of the present invention is, in an electronic control
unit, to improve operational reliability against heat while
suppressing increase in size and increase in manufacturing cost of
the electronic control unit.
According to the present invention, in an electronic control unit,
a drive circuit board holding a drive element for supplying power
to an outside control object is disposed on a drive circuit board,
and a control processing element for outputting a control signal to
the drive element to control the outside control object is disposed
on a control circuit board. A connector through which a signal is
inputted into the control processing element and the power is
supplied to the outside control object is further disposed on the
control circuit board. The drive circuit board and the control
circuit board are disposed in a box to face each other and
connected by a connecting wire.
Preferably, the connecting wire is connected to the control circuit
board at a bonding portion in a vicinity of the connector. The
connecting wire can be bonded to mutually facing end parts of the
control circuit board and the drive circuit board, be bent to form
a gap with a wall of the box, and have a length that allows the
control circuit board and the drive circuit board to be lined up in
an identical plane without an overlap.
Preferably, the control processing element and the drive element
are disposed at opposite sides to each other with a plane
interposed therebetween, the plane being approximately
perpendicular to an inner wall of the box on which the drive
circuit board is disposed.
According to the present invention described as above, heat
generated in the drive element is suppressed from being transferred
to the control processing element, and the operational reliability
against heat of the electronic control unit is improved while
suppressing increase in size and increase in manufacturing
cost.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects and features of the present invention will become
more readily apparent from a better understanding of the preferred
embodiments described below with reference to the following
drawings, in which;
FIG. 1A is an explanatory view showing a conventional electronic
control unit as seen from a direction parallel with a circuit
board;
FIG. 1B is an explanatory view showing the conventional electronic
control unit as seen from a direction perpendicular to the circuit
board;
FIG. 2A is an explanatory view showing an electronic control unit
as seen from a direction parallel with a control circuit board in a
first preferred embodiment;
FIG. 2B is an explanatory view showing the electronic control unit
as seen from a direction perpendicular to the control circuit board
in the first embodiment;
FIGS. 3A and 3B are cross-sectional views schematically showing
drive elements;
FIG. 4 is an explanatory view for explaining an example of how
signals flow in the control circuit board and a drive circuit board
connected to each other with a flexible board;
FIGS. 5A to 5C are explanatory views showing a procedure for
connecting the control circuit board and the drive circuit board
with the flexible board;
FIG. 6 is an explanatory view showing an electronic control unit as
seen from a direction parallel with a control circuit board in a
second preferred embodiment;
FIGS. 7A and 7B are explanatory views showing modified electronic
control units in the second embodiment;
FIGS. 8A to 8C are explanatory views showing another embodiment of
an electronic control unit pertaining to the invention.
FIG. 9A is an explanatory view showing an electronic control unit
as seen in a direction parallel with a control circuit board in a
third preferred embodiment;
FIG. 9B is an explanatory view showing the electronic control unit
as seen in a direction perpendicular to the control circuit board
in the third embodiment;
FIG. 10A is an explanatory view showing an electronic control unit
as seen in a direction parallel with a control circuit board in a
fourth preferred embodiment;
FIG. 10B is an explanatory view showing the electronic control unit
as seen in a direction perpendicular to the control circuit board
in the fourth embodiment;
FIG. 11 is an explanatory view showing a modified electronic
control unit in the fourth embodiment;
FIG. 12A is an explanatory view showing a modified electronic
control unit as seen in a direction parallel with a control circuit
board in the present invention; and
FIG. 12B is an explanatory view showing the modified electronic
control unit as seen in a direction perpendicular to the control
circuit board.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Preferred embodiments of the invention will now be described along
with the drawings.
First Embodiment
FIGS. 2A and 2B show a construction of an electronic control unit 1
in a first preferred embodiment. This electronic control unit 1
performs engine control by driving and controlling various
actuators (control objects such as ignition plugs, electromagnetic
solenoids and so on, not shown) provided in an engine (not shown)
of a vehicle. The electronic control unit 1 has a connector 2, a
control processing element 3 and drive elements 5 (5a, 5b).
The connector 2 is for the electronic control unit 1 to achieve
delivery and receipt of signals between itself and the outside
control objects. The control processing element 3 of this
embodiment is a microcomputer constructed as a so-called one chip
microcomputer, and by way of this connector 2 takes in input
signals from various sensors detecting the running state of the
engine, carries out control processing (computational processing)
based on those input signals, and outputs control signals
corresponding to results of the control processing to the drive
elements 5. The control processing element 3 also carries out
communication with various electronic devices (not shown) mounted
in the vehicle by way of the connector 2.
The control processing element 3 is accommodated inside a box 7
constituting the outer form of the electronic control unit 1, and
is mounted on a control circuit board 9 inside this box 7. The
control circuit board 9 is a resin board (in this embodiment, a
board having glass cloth as a base material, and epoxy resin
impregnated into the base material), for forming a control circuit
for controlling outside actuators. Besides the control processing
element 3 a number of other electronic components (not shown) are
also mounted on this control circuit board 9, and constitute a
predetermined control circuit together with the control processing
element 3.
In the control circuit comprising the control processing element 3,
to take account of the fact that signals from outside sensors (not
shown) and many signals such as communication signals from outside
electronic devices are handled, and to take account of ease of
mounting, the connector 2 is provided on the control circuit board
9. The connector 2 has connector pins 8 for electrically connecting
the connector 2 to a predetermined circuit board, and is
electrically connected to interconnection patterns on the control
circuit board 9 via these connector pins 8. The connector pins 8
are fixed to the control circuit board 9 in a state where the pins
8 are inserted into through holes 9a formed in the control circuit
board 9.
The control circuit board 9 is disposed in parallel with a drive
circuit board 11 (which will be discussed later) so that its board
face and the board face of the drive circuit board 11 face each
other. The connector 2 and the control processing element 3 are
provided on the back side face (i.e. the upper face) of the face
(in FIG. 2A, the lower face) of the control circuit board 9 facing
the drive circuit board 11. Furthermore the connector 2 is disposed
on an end part of the back side face of the control circuit board
9. FIG. 2A shows the construction of the electronic control unit 1
as seen from a direction parallel with the board face of the
control circuit board 9, and FIG. 2B shows the electronic control
unit 1 as seen from a direction perpendicular to the board face of
the control circuit board 9.
The drive elements 5, on the other hand, are for supplying power to
actuators of the engine and driving them. That is, the drive
elements 5 are so-called switching elements and are provided in
power paths leading from an outside vehicle battery (not shown) of
the electronic control unit 1 to the actuators, and cut or make
these power paths on the basis of control signals from the control
processing element 3.
The drive elements 5 also are provided inside the box 7 like the
control processing element 3, but are mounted on a separate board
(the drive circuit board 11) from the control circuit board 9 on
which the control processing element 3 is mounted. This drive
circuit board 11 on which the drive elements 5 are mounted is a
ceramic board having superior thermal radiation property, which is
for forming driving circuits constituting a part of the power paths
for supplying power to the actuators. Various electronic components
(not shown) including the drive elements 5 are mounted on the face
(the upper face) of the drive circuit board 11 facing the control
circuit board 9, whereby predetermined driving circuits are
formed.
As shown in FIGS. 3A and 3B, the drive elements 5 of this
embodiment are so-called bare chip type transistors (ones of a type
wherein semiconductor chips are not received in packages of resin
or the like). The necessary power differs among the actuators that
are the control objects, and because there are also differences in
the amount of heat produced by the respective drive elements 5,
different types of drive elements are sometimes used in
correspondence with differences in power amount (i.e. differences
in amount of heat produced).
That is, when the amount of heat produced is likely to be large, as
shown in FIG. 3A, a type of drive element wherein a semiconductor
chip 6b is mounted on the board through a radiation fin 6a is used
as the drive element 5a. When the amount of heat produced is likely
to be relatively small, as shown in FIG. 3B, another type of drive
element wherein a semiconductor chip 6b is directly mounted on the
board without a radiation fin being interposed therebetween is used
as the drive element 5b. It should be noted that the drive elements
5 includes these different types of drive elements 5a, 5b.
The drive elements 5 are mounted on an interconnection pattern 10
formed on the board 11, and one electrode of each of the drive
elements 5 (in this embodiment a collector electrode) is
electrically connected to the interconnection pattern 10 directly
or by way of the radiation fin 6a. The other electrodes (in this
embodiment, a base electrode and an emitter electrode) are
electrically connected to the interconnection pattern via bonding
wires 6c made of gold or aluminum or the like.
The control circuit board 9 on which is formed the control circuit
comprising the control processing element 3 and the drive circuit
board 11 on which is formed the drive circuit comprising the drive
elements 5 are electrically connected to each other by a flexible
printed circuit board (flexible board) 13 as a connecting wire. The
flexible board 13 has excellent elasticity and is soldered to end
parts of the control circuit board 9 and the drive circuit board 11
to be electrically connected to the interconnection patterns on the
boards 9, 11.
The bonding portion of the flexible board 13 on the control circuit
board 9 is positioned in the vicinity of the connector 2, and
specifically is provided on a back side part of the mounting
location of the connector 2 on the control circuit board 9. The
flexible board 13 is bent into a U-shape having a suitable bend
between the two boards 9 and 11, and is disposed so that a gap is
formed between itself and the box 7 (particularly, a box bottom
part 7b, a box cylindrical part 7c and board support parts 7f,
which will be discussed later). The flexible board 13 is also
disposed so that a gap is provided between the electronic
components mounted on the two boards 9, 11.
Here, FIG. 4 is a view showing the mutually facing faces of the
control circuit board 9 and the drive circuit board 11 that are
connected by the flexible board 13. That is, in FIG. 4, it is shown
from the direction of the upper face of the drive circuit board 11,
but with respect to the control circuit board 9, it is shown in a
state inverted by 180.degree. about the flexible board 13 (that is,
upside down). As will be discussed later, the lower face of the
drive circuit board 11 is provided in close adhesion with the box
bottom part 7b that serves as a radiation plate.
Next, along with this FIG. 4, an example of a flow of signals in
the electronic control unit 1 in this embodiment will be
described.
When a signal from an outside sensor (a sensor signal) is
transmitted to the connector 2, the sensor signal is transmitted to
an input terminal of the control processing element 3 through a
connector pin 8a and an interconnection pattern 15a formed on the
upper face of the control circuit board 9 (that is, the back face
of the face facing the drive circuit board 11). Various signals are
inputted to the control processing element 3 also via paths other
than those shown. Then, the control processing element 3 executes
computational processing based on the various inputted signals, and
outputs control signals for drive-controlling the outside control
objects.
The output signals outputted toward the drive elements 5 from an
output terminal of the control processing element 3 are transmitted
to the flexible board 13 through an interconnection pattern 15b
formed on the upper face of the control circuit board 9, a via hole
17 passing through the control circuit board 9, and an
interconnection pattern 15c formed on the lower face of the control
circuit board 9. In this embodiment, in connection with the fact
that the bonding portion of the flexible board 13 on the control
circuit board 9 is disposed on the back side part of the connector
2, the interconnection pattern 15c is formed to pass through a
space between the connector pins 8.
Then the control signals are transmitted through an interconnection
pattern 19a of the flexible board 13 to the drive circuit board 11,
and further are transmitted through an interconnection pattern 21a
formed on the upper face of the drive circuit board 11 to an input
terminal (in this preferred embodiment, a base electrode) of the
drive element 5b. The drive element 5b is turned on or turned off
in correspondence with the control signals, and makes or breaks the
power path to the outside actuator.
When this drive element 5b is turned on, the power path, which is
composed of an interconnection pattern 21b formed on the upper face
of the drive circuit board 11, an interconnection pattern 19b of
the flexible board 13, and an interconnection pattern 15d formed on
the lower face of the control circuit board 9 and an connector pin
8b and so on, is made, and powering of that actuator is carried
out. The interconnection patterns 15d, 19b, 21b constituting the
power path of the outside control object are formed wider in width
than the interconnection patterns 15a through 15c, 19a, 21a
constituting the transmission path of sensor signals and control
signals to prevent heat generation and voltage drop even when a
large current is passed through.
The control circuit board 9 and the drive circuit board 11
connected to each other in this way are received in the box 7 as
shown in FIG. 2A. The walls of the box 7 receiving these two boards
9, 11 are made by casting a metal (in this embodiment, aluminum),
and are made up of a box lid part 7a, the box bottom part 7b and
the box cylindrical part 7c.
The box lid part 7a is formed as a cylindrical body having one end
(closed end) closed, and has a side face opening 7d formed in a
side face part of the cylindrical body for exposing the connector 2
to the outside. At the opposite end of the box lid part 7a to the
above-mentioned closed end, an end opening 7e of substantially the
same shape as the control circuit board 9 is formed, and the
control circuit board 9 can be fitted in that end opening 7e. When
the control circuit board 9 is fitted in the end opening 7e, the
box lid part 7a covers the face of the control circuit board 9 on
which the connector 2 is mounted.
The box bottom part 7b is disposed on the opposite side of the
control circuit board 9 from the box lid part 7a, with the box
cylindrical part 7c interposed therebetween. The box bottom part 7b
is for making it easy for heat produced in the electronic control
unit 1 (particularly the drive elements 5) to be released to
outside the box 7, and is constructed as a thick (for example
thicker than the box lid part 7a) radiation plate so that it can
absorb heat swiftly. The drive circuit board 11 is mounted in close
adhesion with the inner surface of the box bottom part 7b (the
upper side in FIG. 2A) so that heat produced in the drive elements
5 is efficiently released by the box bottom part 7b. That is, the
box bottom part 7b forms the wall constituted as a radiation
plate.
The box cylindrical part 7c is formed as a cylindrical body with a
cross-section having the same shape as the box lid part 7a and both
ends open, and is connected to the box lid part 7a and the box
bottom part 7b at the two ends. The box cylindrical part 7c, as
shown in FIG. 2A, constitutes a side face part of the box 7
together with the box lid part 7a, and cuts off the space between
the control circuit board 9 and the drive circuit board 11 (that
is, the control circuit board 9 and the box bottom part 7b) from
the space outside the box 7. Board support parts 7f for supporting
the control circuit board 9 are provided on the box cylindrical
part 7c.
To assemble the electronic control unit 1 having the construction
described above, it is preferably carried out with the order
explained next (see FIGS. 5A to 5C). First, electronic components
including the drive element 5a are mounted on the drive circuit
board 11 to form a predetermined drive circuit. Then, the lower
face of the drive circuit board 11 with the drive circuit mounted
on it (that is, the back side face of the face on which the drive
elements 5 are mounted) is brought into close adhesion with the box
bottom part 7b serving as a radiation plate as shown in FIG.
5A.
To bring the drive circuit board 11 into close adhesion with the
box bottom part 7b, the two are brought face to face with an
adhesive having superior thermal conductivity therebetween, and
held for a predetermined time (for example about 30 minutes) at a
high temperature (for example about 150.degree. C.). By thermally
hardening the adhesive in this way, the drive circuit board 11 and
the box bottom part 7b are bonded in close adhesion and the thermal
resistance between the drive circuit board 11 and the box bottom
part 7b is made small.
For the control circuit board 9 also, various electronic components
including the connector 2 and the control processing element are
mounted on it to form a predetermined control circuit.
Next, the drive circuit board 11 adhered to the box bottom part 7b
and the control circuit board 9 are disposed lined up in the same
plane S. At this time, the faces of the two boards 9, 11 to be
facing each other are made to face in the same direction. Then as
shown in FIG. 5B, from one side of that plane S (specifically, the
side of the faces of the two boards 9, 11 which are to face each
other), the flexible board 13 is brought close, and is bonded by
soldering and thermo compression bonding to the adjacent end parts
of the two boards 9, 11 disposed side by side. The flexible board
13 is bonded to the two boards 9, 11 by applying solder to the
surfaces of the two boards 9, 11, which are to become these bonding
portions, and by melting the solder with the flexible board 13
pressed against it with a pre-heated crimping jig (not shown).
After that, as shown in FIG. 5C, by the drive circuit board 11 (or
the control circuit board 9, or the two boards 9, 11) being turned
about the flexible board 13, the two boards 9, 11 are made to face
each other (that is, so that they overlap), and received inside the
box 7 described above.
With the electronic control unit 1 of this embodiment constructed
as described above, the following effects are obtained.
Because the drive elements 5 and the control processing element 3
are mounted on the mutually different separate boards 9, 11, heat
transmitted from the drive elements 5 to the control processing
element 3 can be reduced. Because of this, even if, in the future
the power handled by the drive elements 5 increases, or the number
of drive elements 5 increases so that the amount of heat produced
in the drive elements 5 increases, the influence of heat reaching
the control processing element 3 can be suppressed.
Because the box bottom part 7b of the electronic control unit 1 is
constructed as a radiation plate and the drive circuit board 11
with the drive elements 5 mounted on it is provided in close
adhesion with the inner side surface of this box bottom part 7b
serving as a radiation plate, even if the drive elements 5 produce
heat, through the radiation plate the heat can be swiftly
discharged to outside the box 7 (that is, outside the electronic
control unit 1). Because of this, the influence on the control
processing element 3 of heat produced by the drive elements 5 can
be further suppressed, and rising in temperature of the drive
elements 5 can also be suppressed.
Because the control circuit board 9 and the drive circuit board 11
are disposed to face each other, the increase in size of the
electronic control unit 1 can be suppressed. The bonding portion of
the flexible board 13 on the control circuit board 9 is provided in
the vicinity of the connector 2. Specifically, the connector 2 is
mounted on the back side face of the face of the control circuit
board 9 facing the drive circuit board 11 and the flexible board 13
is bonded to the control circuit board 9 at the back side part of
the connector 2.
Because of this, layout hindrances, which can arise due to the
flexible board 13 being bonded to the control circuit board 9, can
be greatly reduced. The area of the interconnection pattern for the
power path on the control circuit board 9 can be reduced, and
accordingly, the circuit design for the control circuit board 9
becomes easy. Because the path length between the drive element 5
and the connector 2 is shortened, the voltage drop between the two
can also be suppressed.
Further, because the back side part of the connector 2 on the
control circuit board 9 usually holds parts as noise
countermeasures and the interconnection patterns leading from the
connector 2 to the control processing element 3 are few on the back
side part, the degree of freedom on design is high for the parts
and interconnection patterns. Therefore, bonding the flexible board
13 to the back side part of the connector 2 greatly decreases the
limitation of layout on design.
Because the connector 2 is mounted on the control circuit board 9
at the back side face of the face facing the drive circuit board
11, the face to which the flexible board 13 is bonded faces the
drive circuit board 11. Because of this, the control circuit board
9 and the drive circuit board 11 can be connected to overlap with
each other (that is, to face each other) without hindrance.
Because the connector 2 is mounted on the end part of the control
circuit board 9 and the flexible board 13 also is bonded to the end
parts of the two boards 9, 11, the degree of freedom of layout of
interconnection patterns and electronic components (including also
the control processing element 3 and the drive elements 5) can be
made higher. Because the flexible board 13 is used as a connecting
wire for connecting the control circuit board 9 and the drive
circuit board 11, making small of the electronic control unit 1 can
be further promoted, and the number of parts can be reduced.
However, it is apparent that several separate wires or the like can
be used instead of the flexible board 13 for connecting the two
boards 9, 11.
Of the interconnection patterns formed on the flexible board 13,
the interconnection pattern 19b forming the power path leading from
the drive elements 5 through the connector 2 to the control object
is made wider in width than the interconnection pattern 19a forming
the control signal transmission path leading from the control
processing element 3 to the drive elements 5. This is because in
the transmission path the control signal flows with a small
current, and in the power path a large current flows for supplying
power to the control objects. Thus, it is possible to prevent
voltage drop and heat generation in the flexible board 13 while
suppressing increase in size of the flexible board 13, by changing
the widths of the interconnection patterns in accordance with the
magnitudes of current flowing in the patterns.
When the control circuit board 9 and the drive circuit board 11 are
electrically connected to each other, the drive circuit board 11
and the control circuit board 9 are lined up in the same plane and
the flexible board 13 is bonded to the mutually adjacent end parts
of the two boards 9, 11 disposed in this state by soldering and
thermo compression bonding from one side of that plane. With this
method, because the electrical connection of the two boards 9, 11
can be achieved simply, and the manufacturing process of the
electronic control unit 1 can be made a simple one. By extension it
is possible to suppress its manufacturing cost.
Because the drive circuit board 11 is brought into close adhesion
with the box bottom part 7b before the control circuit board 9 and
the drive circuit board 11 are connected to each other with the
flexible board 13, the manufacturing process of the electronic
control unit 1 can be made a more simple one. Further, because the
bonding of the drive circuit board 11 to the box bottom part 7b,
i.e., the radiation plate generally requires a high temperature
(about 150.degree. C. in this embodiment) for hardening the
adhesive, it is preferable to perform the bonding without the
control circuit board 11 not to cause deficiencies on the control
circuit board 11.
The flexible board 13 is bonded to the mutually facing end parts of
the two boards 9, 11 and is bent to form a gap between itself and
the box 7. Further, the flexible board 13 has a specific length
that allows the two boards 9, 11 to be disposed lined up in the
same plane S not to overlap each other in a state where the boards
9, 11 are mutually connected as shown in FIGS. 5B and 5C.
Accordingly, the two boards 9, 11 can be connected by a simple
process. As a result, the manufacturing process of the electronic
control unit 1 can be made simple, and manufacturing cost can be
suppressed.
Because the flexible board 13 is bent between the mutually facing
boards 9, 11 to form a gap between itself and the wall face of the
box 7, the flexible board 13 and the bonding portions between the
flexible board 13 and the respective boards 9, 11 are suppressed
from undergoing stress, and simultaneously the flexible board 13 is
prevented from being damaged by rubbing with the box 7 caused by
vibrations or the like from the outside.
Further, because the flexible board 13 is bent into a U-shape, even
when a force of some kind is applied to the flexible board 13, the
force can be dispersed to the entire portion of the flexible board
13. The force is difficult to be applied to the flexible board 13
locally, so that deficiencies of electrical connection such as
breakages on the flexible board 13 can be prevented. It is
undesirable that the flexible board 13 is stretched between the two
boards 9, 11 such that tensile stress is applied to the bonding
portions of the flexible board 13. Furthermore, the flexible board
13 is provided so that a gap is provided between the electronic
components mounted on the two boards 9, 11. Therefore, the flexible
board 13 is difficult to contact the electronic components, and
accordingly the possibility of causing deficiencies to the flexible
board 13 and the electronic components is lowered.
Second Embodiment
Next, a second preferred embodiment of the present invention will
be explained in which the same parts and components as in the first
embodiment are indicated with the same reference numerals.
In the electronic control unit 1 in the second embodiment as shown
in FIG. 6, the control circuit board 9 and the drive circuit board
11 are mutually connected by a flexible board 14, instead of the
flexible board 13 in the first embodiment. The flexible board 14
has several folds at specific portions (three portion in this
embodiment) between a bonding portion 15 with the control circuit
board 9 and a bonding portion 16 with the drive circuit board 11.
The flexible board 14 is bent to have a first folded portion 14a, a
second folded portion 14b, and a third folded portion 14c in this
order from the side of the boding portion 15 with the control
circuit board 9.
The first folded portion 14a is formed by the fold closest to the
bonding portion 15 with the control circuit board 9, and protrudes
in a direction progressing from the projecting portions 8c of the
connector pins 8 toward the bonding portion 15. The third folded
portion 14c is formed by the fold farthest from the bonding portion
15 with the control circuit board 9 (that is, closest to the
bonding portion 16 with the drive circuit board 11), and protrudes
in the direction progressing from the projecting portions 8c of the
connector pins 8 toward the bonding portion 15. The second folded
portion 14b is formed by the fold provided between the fold forming
the first folded portion 14a and the fold forming the third folded
portion 14c, and protrudes in the direction progressing from the
bonding portion 15 toward the projecting portions 8c of the
connector pins 8.
Because the second folded portion 14b is formed into a shape
protruding in the direction progressing from the bonding portion 15
toward the projecting portions 8c of the connector pins 8, the
flexible board 14 has a possibility to contact the projecting
portions 8c of the connector pins 8. In this connection, the second
folded portion 14b should be located at the side of the bonding
portion 15 between the flexible board 14 and the control circuit
board 9 with respect to the projecting portions 8c of the connector
pins 8. The electronic control unit 1 of this second embodiment is
constructed such that all of the folded portions 14a, 14b, 14c are
positioned at the side of the bonding portion 15 between the
flexible board 14 and the control circuit board 9 with respect to
the projecting portions 8c of the connector pins 8.
The other features of the electronic control unit 1 in the second
embodiment are substantially the same as those in the first
embodiment, and those explanations are omitted.
According to the electronic control unit 1 constituted as above in
the second embodiment, in addition to the effects described in the
first embodiments, the following effects are provided.
The flexible board 14 is formed with several folds in advance, and
is disposed between the two boards 9, 11 in a state where it is
bent at the respective folds. Therefore, the shape of the flexible
board 14 to be formed between the two boards 9, 11 facing each
other can be determined in advance. The flexible board 14 therefore
can be securely prevented from contacting the wall face of the box
7.
The folded portions of the flexible board 14 is positioned at the
side of the bonding portion 15 between the flexible substrate 14
and the control circuit board 9 with respect to the projecting
portions 8c of the connector pins 8. Therefore, the flexible board
14 can be prevented from contacting the projecting portions 8c of
the connector pins 8 inserted into the through holes 9a of the
control circuit substrate 9, and from being damaged by the
connector pins 8.
Although in the electronic control units 1 of the first and second
embodiments, the flexible board 13, 14 is connected to the control
circuit board 9 in the vicinity of the connector 2, it is not
limited to this. The flexible board 13, 14 may be bonded to a
location apart from the connector 2 (for example, as shown in FIGS.
7A and 7B, an end part at an opposite side of the connector 2). In
this case also the flexible board 13, 14 is provided to form gaps
with the wall face of the box 7, and the electronic components
mounted on the boards 9, 11 not to contact these parts.
Although in the embodiments described above, as shown in FIGS. 3A
and 3B, the bare chip type transistors are used as the drive
elements 5, it is not limited to this. For example, as shown in
FIG. 8A, a drive element 5c of a type (a so-called molded type)
wherein resin is molded around a semiconductor chip 6b can be used.
The molded type drive element 5c shown in FIG. 8A has an electrode
lead 6d fixed in a resin part 6e together with the semiconductor
chip 6b, and is connected to an interconnection pattern 10 via the
electrode lead 6d and a radiation fin 6a. The electrode lead 6d is
connected to the semiconductor chip 6b via a bonding wire 6c, and
the radiation fin 6a is connected to the semiconductor chip 6b
directly. Even when this kind of drive element 5c is used, the
electronic control unit 1 of the embodiments described above can be
constructed substantially in the same way as shown in FIGS. 8B and
8C.
Third Embodiment
A third preferred embodiment of the present invention will be
explained referring to FIGS. 9A and 9B in which the same parts and
components as in the first embodiment are indicated with the same
reference numerals.
As shown in FIGS. 9A and 9B, in the third embodiment the control
processing element 3 mounted on the control circuit board 9 and the
drive element 5 mounted on the drive circuit board 11 are disposed
separately from each other. Specifically, assuming a virtual plane
T perpendicular to the wall face of the drive circuit board 11 (box
bottom part 7b), the control processing element 3 and the drive
element 5 are positioned at opposed sides to each other with the
plane T intervening between the two. The connector 2 and the drive
circuit board 11 are also disposed at the side of the drive circuit
board 5 with respect to the virtual plane T between the two
elements 3, 5, and are mutually connected by the flexible board
13.
According to this third embodiment, because the two elements 3, 5
are disposed not to overlap each other in the direction
perpendicular to the drive circuit board 11, heat is suppressed
from being transferred from the drive element 5 to the control
processing element 3. The size of the electronic control unit 1 can
be reduced. Further, the connector 2 is disposed at the side of the
drive element 5 with respect to the virtual plane T. Because of
this, the power path between the drive element 5 and the connector
2 can be shortened, and voltage drop, i.e., power loss can be
suppressed. The other features and effects are substantially the
same as those in the first embodiment.
Fourth Embodiment
In a fourth preferred embodiment of the present invention, as shown
in FIGS. 10A and 10B, a resin-made heat interception plate 20 is
provided, along the virtual plane T, in a space defined between the
wall face as a radiation plate (box bottom part 7b) on which the
drive circuit board 11 is mounted and the control circuit board 9.
The heat interception plate 20 is shaped generally into an L-shape,
and has a base part (forming a bottom part of the L-shape) disposed
directly on the box bottom part 7b being provided as the radiation
plate.
The heat interception plate 20 divides the space defined between
the box bottom part 7b and the control circuit board 9 into two
spaces (space A containing the drive element 5 and space B in the
vicinity of the control processing element 3). That is, the heat
interception plate 20 intercepts convection flowing between the
space A at the drive element side and the space B at the control
processing element side. Accordingly, atmosphere having received
heat of the drive element 5 is prevented from approaching the
vicinal region of the control processing element 3.
According to the fourth embodiment, heat transfer from the drive
element 5 to the control processing element 3 due to the convection
of atmosphere can be suppressed. Radiation heat can also be
prevented from being transferred from the drive element 5 to the
control processing element 3.
Because the heat interception plate 20 is made of resin being a
material having a low thermal conductivity, thermal conduction from
the space A at the drive element side to the space B at the control
processing element side can be further suppressed. Also, heat is
suppressed from being transferred from the drive circuit board 11
(the box bottom part 7b as the radiation plate) to the control
circuit board 9 through the heat interception plate 20. The other
features and effects are substantially the same as those in the
above embodiments.
Although in the electronic control unit 1 of the fourth embodiment
it is explained that the heat interception plate 20 is provided
along the virtual plane T perpendicular to the box bottom part 7b
holding the drive circuit board 11 thereon, it is not limited to
this. The heat interception plate 20 can have various shapes and be
determined in accordance with the layout of the electronic
components mounted in the box 7 as long as the convection is
prevented from flowing between the space in the vicinity of the
drive element 5 and the space in the vicinity of the control
processing element 3.
Although in the electronic control unit 1 in the third and fourth
embodiments, the connector 2 is provided at the side of the drive
element 5 with respect to the virtual plane T, it is not limited to
this. For example as shown in FIG. 11, the connector 2 may be
provided at the side of the control processing element 3.
Also in the third and fourth embodiments, the drive elements 5 are
not limited to the bare chip type transistors shown in FIGS. 3A and
3B, and for example a drive element 5c of a type (a so-called
molded type) shown in FIG. 8A wherein resin is molded around a
semiconductor chip 6b can be used as in the other embodiments. Even
when this kind of drive element 5c is used, for example the
electronic control units 1 can be constructed substantially in the
same way as in the embodiments above as shown in FIGS. 12A and
12B.
In the electronic control unit of the embodiments described above,
it is described as one for driving and controlling actuators
provided in an engine of a vehicle, but it is clear that it is not
limited to this.
While the present invention has been shown and described with
reference to the foregoing preferred embodiments, it will be
apparent to those skilled in the art that changes in form and
detail may be made therein without departing from the scope of the
invention as defined in the appended claims.
* * * * *